Recently, two-dimensional (2D) materials such as graphene, graphene oxide (GO), metal-organic framework (MOF) nanosheet, and zeolite nanosheet (MFI crystal type) have been widely utilized for membrane applications in water purification, gas separation, and even for a separator in the battery. The fast expansion of membrane technology and science based on the 2D materials can be attributed to several reasons. First, precise molecular sieving or selective molecular transport can be achieved by the interlayer spacing of stacked nanosheets or by its atomic pore structure. And abundant surface functional groups can interact with penetrating molecules affecting the solubility and diffusivity. Second, large aspect ratio, excellent mechanical and chemical stability of the nanosheets easily allow the fabrication of defect-free ultrathin film (thickness of nanometer scale) on a porous support, which enhances the flux of water or gas molecules. Most of all, some of the 2D materials are easy to prepare by the well-established synthesis method like Hummer’s method for graphene oxide and solvent-based exfoliation for other 2D materials.

In this talk, the key factors to design graphene oxide membrane with ultra-fast water flow will be discussed: dimension of nanomaterials, support structure, interlayer chemistry, and intercalating molecules. The high-performance nanofiltration membrane is feasible using the stacked structure of GO, and the performance is surpassing commercial polymer-based nanofiltration membranes. In addition, a new method to prepare bulk-scale MFI nanosheets (5.5Å of pore diameter) will be presented. The synthesis was achieved by using the confinement effect of graphite in a synthesis solution. While multi-lamellar MFI is highly branched due to the intergrowth of MFI nanosheets, the intergrowth was hindered in the confined space between graphite flakes, resulting in MFI particles composed of stacked silicalite-1 nanosheets. The thickness of nanosheet was around 20 nm and diameter ranged from sub-micrometer and even up to 10 μm (aspect ratio: 500). Mixed matrix membrane was fabricated by infiltrating PDMS into a laminated MFI nanosheet film. The membrane showed n-butane permeability of c.a. 2800 barrer and n-butane/i-butane ideal selectivity of 21, which is surpassing the upper bound of polymer and mixed matrix membranes. And the permeability is c.a. 3 order faster than highly n-butane selective polymer (6FDA-DAM) with similar ideal selectivity.